1. Field of the Invention
This invention relates to valves and particularly to a new and improved valve which is magnetically actuated and which virtually eliminates fluid leakage to the outside of the fluid system.
2. Description of the Prior Art
Valves are used to control the flow of fluid through piping. A problem encountered with valves, however, is leakage of fluid through penetrations in the valve body, or outer shell of the valve, such as where the valve stem protrudes. Often, the valve body itself is fabricated of several sections which are bolted or threaded together, such valve body interfaces providing other potential leak paths for the fluid.
The wearing down of seals within a valve also contributes to leakage of fluid across the seal and to the outside of the fluid system. Dynamic seals, that is, seals which must block fluid flow while permitting relative motion between sealing members as the valve is opened or closed, tend to wear out faster than static seals, which block fluid flow only upon compression between sealing members. Thus, many typical currently used valves which employ multi-piece valve bodies having penetrations therethrough and dynamic seals therein are prone to fluid leakage, resulting in more frequent valve replacement and higher cost to the user.
Magnetically operated valves have been developed to help alleviate fluid leakage. Many, however, use multi-section valve bodies resulting in potential leak paths between sections. Such valves also often use conventional screw and nut arrangements to transform rotational motion of an actuating magnet into linear motion of a sealing member. Oversize and very expensive magnets may be required to rotate the screw in the nut, however, and the closing force available may be relatively small because of the high amount of sliding friction encountered between the male and female threads of the screw and nut.
In view of the above-mentioned problems, it is therefore an object of the present invention to provide a valve with virtually no external leakage by eliminating all penetrations through the valve body.
Another object of the present invention is to increase the useful service life of a valve by employing only static seals therein and by utilizing a simple valve drive mechanism.
Yet another object of the present invention is to provide a magnetically actuated valve employing a low friction screw and nut arrangement thereby allowing smaller, less expensive magnets to be used for actuation or, alternatively, obtaining a comparatively greater actuation force from standard magnetic materials.